A demodulation reference signal (DMRS) is a reference signal of an uplink physical channel in a communications system. A network device needs to complete estimation of an uplink data channel by using the DMRS, so as to complete data demodulation. In different systems, terminal device performance and redundancy overheads need to be comprehensively considered in a design of a DMRS time domain density, so as to meet a specific scenario requirement.
In the prior art, for a communications system, a DMRS time domain density is fixed, and a network device cannot configure a DMRS with a proper time domain density for the terminal device based on a current movement speed of the terminal device. However, in some application scenarios, for example, cellular Internet of Things (CIoT), a movement speed of the terminal device has a specific dynamic range. If a DMRS time domain density is relatively low for the terminal device, the network device cannot track a time-varying channel of the terminal device and implement coherent demodulation of control or data. If a DMRS time domain density is relatively high for the terminal device, DMRS redundancy in a time-frequency resource used by the terminal device is very high.